[Author] I'll weigh in-

MySql, Postgresql [and the other major players] should all leverage the same standardized syntax (they're close, but not drop-in replacements). In this case when one gets acquired the switching cost is 0. In fact, if they follow the same query contract you could database-dump from one to the other.

Which one shouldn't have existed? Whichiver came second, I suppose. I don't understand why the authors between the two wouldn't cooperate and build one open-source system and fork it if it got acquired.